Fluid transport systems are well known and used in a number of applications. One specific application of transporting a fluid in a machine is the transportation of ink in a printer. Common examples of inks include aqueous inks and phase change or solid inks. Aqueous inks remain in a liquid form when stored prior to being used in imaging operations. Solid ink or phase change inks typically have a solid form, such as pellets or as ink sticks, which are inserted into feed channels in a printer through openings to the channels. After the ink sticks are fed into the printer, the ink sticks are urged by gravity or a mechanical actuator to a heater assembly of the printer. The heater assembly includes a heater positioned proximate to a melt plate to heat the melt plate to a temperature that melts an ink stick contacting the melt plate. The melt plate can be oriented to drip melted ink into a reservoir and the ink stored in the reservoir continues to be heated until the ink is fed to an inkjet ejector.
Fluid couplings in the printer supply the liquid ink held in each reservoir of colored ink to one or more printheads in the inkjet printing apparatus. The liquid ink is pumped from the reservoir to a manifold in the inkjet printing apparatus. As the inkjets in the printheads eject ink onto an image receiving member, the action of the diaphragms in the inkjets pulls ink from the manifold. Various embodiments of inkjets include piezoelectric and thermal devices that are selectively activated electrical firing signals received from a controller.
Phase change ink printers often include one or more heaters that generate heat to maintain a supply of phase change ink in a liquid state in the printheads and inkjets for use during printing operations. Typically, the heaters are electrical heaters that consume electrical energy to generate the desired amount of heat. In order to reduce energy usage, phase change ink printers deactivate various components, including heaters, in the printer during a sleep mode to conserve energy. The ink held in the printheads and inkjets cools and solidifies when the heaters are deactivated.
While sleep modes enable a printer to operate with reduced electrical energy consumption, the solidification of phase change ink within the printer presents difficulties in printing high quality documents when the printer emerges from sleep mode. As phase change ink within an inkjet printing apparatus cools and solidifies, the ink contracts, allowing air into the pressure chambers and fluid conduits within the printheads. As the solidified ink heats and liquefies during a subsequent warm-up process, the air forms bubbles in the liquefied ink that can interfere with operation of the inkjets in the printhead. Additionally, during the warm-up process, both the ink and air bubbles expand due to the heat applied to the printheads. The expanding air bubbles may force some ink through the ejector nozzles, which is referred to as “drooling.” The drooled ink can contaminate other nozzles in the printheads or separate from the printheads and produce errant marks on the image receiving member.
To eliminate air bubbles in the liquefied ink within the printheads and to clear contaminants from the inkjet nozzles and external face of each printhead, the inkjet printing apparatus undergoes a “purge” operation, during which pressure applied to the printheads urges the liquid ink and the air bubbles through the nozzles of the inkjets. In a purge operation, the inkjets emit a stream of ink that flows down the face of the printhead and is collected in a waste ink receptacle. The purge operation removes air bubbles from the inkjets in the printheads and other fluid conduits in the inkjet printing apparatus.
In some printing apparatus designs, a wiping operation occurs after the purge operation. In a wiping operation, a wiper blade engages the face of a printhead and moves across the printhead face. The wiper blade cleans residual ink and contaminants that remain on the face of the printhead after the purge operation. In existing printers, the purged ink and ink from a wiping operation is typically collected in a waste reservoir and is eventually discarded. In printers that enter sleep modes more often to reduce electrical energy consumption, the number of purge cycles and the corresponding amount of discarded ink increases. Thus, improvements to phase change ink printers that reduce or eliminate discarded ink produced during purge cycles are desirable.